In a gas laser oscillator, a dielectric discharge tube is generally formed of ceramics or quartz, a pair of electrodes are arranged on the outer surface of the discharge tube, and a high-frequency ac power is applied to these electrodes to excite gas in the discharge tube to thereby cause an electric discharge. Reflecting mirrors are provided separately on opposite sides of the discharge tube to thus form a laser oscillator.
The electrodes may be formed by a metal deposition process or by bonding a metallic tape to the surface of the discharge tube.
When the ac power is applied to the discharge tube to cause an electric discharge, however, the temperature inside the discharge tube rises, and as a result, the discharge tube temperature reaches 300.degree. C. or thereabouts. Accordingly, a problem has arisen in that the electrodes are separated due to the difference in coefficient of thermal expansion between a dielectric constituting the discharge tube and a metal constituting the electrodes. Moreover, as the temperature of the electrode rises, the temperature of the ambient air rises, and thus a corona discharge occurs at the end portions of the electrodes, which causes a deterioration of the electrodes.
Therefore, to prevent a separation of the electrodes, a cushion is conventionally interposed between the electrodes and the discharge tube, and to prevent the corona discharge, a molded material, such as silicone, is applied to the end portions of the electrodes.
These processes require a reprocessing of the discharge tube, and the manufacture of the discharge tube requires substantial man-hours.